Data exfiltration, also called data extrusion, is the unauthorized transfer of data from a computer. Such a transfer may be manual and carried out by someone with physical access to a computer or may be automated and carried out through malicious programming over a data network.
Malicious exchange of data generally introduces to or extracts data from a computer in an undesirable manner. For example, malicious exchange of data occurs not only in the form of data exfiltration but also in instructing a computer to operate in an undesirable manner known as beaconing in from a Botnet Command and Control server, causing data manipulation in a data network in an undesirable manner, or causing a computer or service to malfunction.
Often, malicious exchange of data occurs by masquerading as a benign or other expected data communication in a data network. For example, the malicious data may be hidden in a data packet intended for some other purpose which is normally regarded as benign in the data network. For example, Domain Name System (DNS) protocol describes the structure and contents of data packets used for data communication between a computer and a DNS server to resolve names of other computers or services.
The domain name resolution according to the DNS protocol is a routine communication that occurs between computers in a data network and one or more DNS servers inside and/or outside the data network.